Ratatoskr is a tiny HTTP server that knows enough WebDAV, CalDAV and CardDAV to be able to replace various cloud services.
The Ratatoskr server is written in MicroPython, with minimal dependencies (just the built-in modules and libc). It also runs in Python 2.x and Python 3.x.
Ratatoskr has a built-in file manager, with viewers for HTML, plain text, markdown, CSV, PDF, OpenDocument, RFC822 messages, JPEG, PNG and SVG images, MP4 videos, and MP3 files. You can see a demo at https://ratatoskr.co.uk.